This invention relates to a filter assembly for filtering fluid, such as working fluid for an automatic transmission of an automobile and to a process for producing the filter assembly.
For filtering engine lubricating oil of an automobile, a filter assembly, in which a filter element is housed in a cylindrical filter case and the filter case is detachably attached to an exterior of an engine block of the automobile, has been typically used. On the other hand, a filter assembly for filtering the working fluid of the automatic transmission of the automobile (herein after called AT-fluid) is normally housed in an interior of a mission case because of limitations with respect to layout in the engine room of the automobile.
However, it has recently tried to detachably attach the filter assembly for the AT-fluid to the exterior of the mission case in order to facilitate maintenance or replacement as in the case of the filter assembly for the engine lubricating oil. In this case, since the pressure of the fluid to be filtered is relatively higher than that of the engine lubricating oil, e.g. the former is twice or three times as much as the later, and pressure fluctuation frequently occurs in the filter assembly, it is necessary to take particular measures to prevent leakage of the fluid in the filter assembly.